1. Field of the Invention
The present invention is related to a lens controlling device that uses a photo reflector as lens position detecting means, and the present invention is also related to an imaging apparatus using the same.
2. Description of Related Art
JP-A-2002-357762 (hereinafter, referred to as Patent Document 1) discloses a camera that is provided with a zoom lens and in which the position of the zoom lens is detected and controlled by using a photo reflector.
Also, JP-A-2001-16496 (hereinafter, referred to as Patent Document 2) discloses a digital imaging apparatus that detects the dark current of a photo-detector array, and corrects aberration (change in thickness of lens elements that constitute a lens system and change in distance between the lens elements) induced by temperature change.
However, conventional lens controlling devices that use a photo reflector as lens position detecting means suffer from the disadvantage that the temperature characteristic of the photo reflector (see FIG. 7) prevents a lens from being driven to its correct target position.
Note that the conventional art disclosed in Patent Document 2 merely corrects aberration of a lens system induced by temperature change, and thus the problem that it aims to solve is different from the problem that the present invention aims to solve, which is compensating for the temperature characteristic of a photo reflector.
In addition, in the conventional art disclosed in Patent Document 2, aberration of a lens system is corrected based on the dark current of a photo-detector array, and thus it is different, in essential features, from the present invention which generates temperature correction signals from the output signal (a photo-electric current) of a photo reflector. In a case where the conventional art of Patent Document 2 is applied as it is as means for compensating for the temperature characteristic of a photo reflector, it is necessary to measure the dark current of the photo reflector. Thus, in order to compensate for the temperature characteristic of the photo reflector while it is operating (i.e., while reflected light is being received), in addition to a light receiving element for measuring a photo-electric current, there must be provided a light receiving element for measuring a dark current, and this invites increase in size and cost of the photo reflector. On the other hand, if the photo reflector includes only a single light receiving element, the measurement of a dark current must be carried out while the photo reflector is not operating, and this makes it impossible to deal with a temperature change occurring while the photo reflector is operating, and thus degrades the accuracy of lens control.